In a liquid crystal display device which is a typical flat-panel-type display, a liquid crystal material 540 is, as shown in FIGS. 28 and 29, enclosed between a transparent substrate 509 in which data lines (source lines) 502a, 502b . . . for supplying an image signal and gate lines 503a, 503b . . . for transmitting a scanning signal are disposed to form a lattice and each of pixel regions 501aa, 501ab, 501ac, 501ba, 501bb, 501bc, 501ca, 501cb, 501cc . . . is sectioned and formed, and another transparent substrate 530 (an opposite substrate) on which a common electrode 533 is formed. By controlling a potential to be applied to a position between common electrode 533 and a pixel electrode 506 of each of the pixel regions 501aa, 501ab . . . via a thin-film transistor (TFT) 508, the state of orientation of the liquid crystal in each of the pixel regions 501aa, 501ab . . . is changed.
A liquid crystal device of the foregoing type encounters a problem in that light leakage (designated by an arrow A) through a gap between, for example, the data line 502a and the pixel electrode 506 deteriorates the display quality. Another problem arises in that a reverse tilt domain region, in which the state of orientation of the liquid crystal becomes disordered due to an influence of an electric field between the data line 502a and the pixel electrode 506, is generated at a position inside of the outer periphery of the pixel electrode 506, and the display quality deteriorates due to this generated region. Therefore, in order to improve the precise clearness of the display of each pixel, a light-shielding black matrix 531 is formed on the other transparent substrate 530 to correspond to a boundary region between pixel regions. Furthermore, the two transparent substrates 509 and 530 are arranged to face each other so as to cause the black matrix 531 to be positioned in the boundary region between the pixel regions so that the quality of display is maintained. If a positional deviation takes place between the boundary regions of the pixel regions and the black matrix 531, the display quality deteriorates. Therefore, the black matrix 531 is given a large marginal width to prevent the foregoing positional deviation.
However, in the circumstance in which the liquid crystal display device has been required to have a larger frame size and to display an image of an improved quality, the conventional arrangement, in which the width of the black matrix is increased, lowers the aperture ratio (the area ratio of a region capable of displaying an image) and thus causes a problem in that the improvement in the display quality is hindered. Accordingly, the inventor of the present invention suggests an arrangement in which the black matrix is formed on the transparent substrate having the active matrix array formed thereon to prevent the positional deviation between the boundary regions of the pixel regions and the black matrix, and to set the width of the black matrix to a minimum width. The inventor of the present invention has first disclosed a liquid crystal display device, described as a comparative example, shown in FIGS. 30 and 31. Referring to these drawings, data lines 502a, 502b . . . and gate lines 503a, 503b . . . are disposed to form a lattice on the surface of a transparent substrate 509 so that each of pixel regions 501aa, 501ab . . . is sectioned and formed. Along the boundary region of each of the pixel regions 501aa, 501ab . . . a black matrix 517 is formed. The black matrix 517 is formed on the surface of a TFT 508 in, for example, a pixel region 501bb, while interposing interlayer insulating films 513 and 515. The TFT 508 is composed of a source 504 to which a data line 502a is electrically connected, a gate electrode 505 to which a gate line 503a is electrically connected, and a drain 507 to which a pixel electrode 506 is electrically connected.
The black matrix 517 is insulated and separated from the data line 502a, the gate 503a and the pixel electrode 506. In the liquid crystal display device constituted as described above, each pixel region and the black matrix 517 can be aligned with each other at an excellent accuracy while eliminating the necessity of providing an unnecessary margin for the width of the black matrix 517. Therefore, the aperture ratio of the liquid crystal device is not sacrificed. However, the liquid crystal display device encounters another problem. Since a potential is not applied to the black matrix 517 and accordingly it is in a floating state, the potential of the black matrix changes depending upon an operational state of the liquid crystal display. The potential change causes the state of orientation of the liquid crystal present between the pixel electrode 506 and the common electrode of the other transparent substrate to become disordered. As a result, the display quality deteriorates. Since the black matrix 517 is commonly used for all of the pixel regions 501aa, 501ab . . . , a short circuit that takes place between the black matrix 517 and any one of the pixel electrodes 506, the data lines 502a, 502b, the gate lines 503a or 503b in the pixel region 501bb will cause a total display defect of the liquid crystal display device.